[MacPorts] #58442: gcc9 (and other gccN) fails to install on Mojave, Xcode-10.2.1

[MacPorts]

#58442: gcc9 (and other gccN) fails to install on Mojave, Xcode-10.2.1
-------------------------+--------------------
  Reporter:  mouse07410  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:
      Port:  gcc9        |
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Comment (by kencu):

 Oh, sure it is. But there will always be wrinkles found, especially if you
 try to ride the fastest horse in the stable.

 To be honest, that is part of the reason someone with Jeremy's skill set
 spends the time to get the newest tools out into the hands of people like
 us -- to find these exact sort of "out in the wild" issues before they
 enter the mainstream of Apple's distributed tools. Jeremy has found
 hundreds of bugs this way, often through our reports, just exactly like
 this one.

 I see there was a commit to the llvm source tree that apparently came
 after the fork to Apple's Xcode 10 version but before llvm/clang-7.0
 release that added this ASSERT. Probably gcc is generating some non-
 standard assembly instructions that previous clang compilers accepted but
 the newer, ever-more-strict compilers do not. Could even be in the
 optimizations of the code rather than the assembly itself. This stuff gets
 pretty mind-bending.

-- 
Ticket URL: <https://trac.macports.org/ticket/58442#comment:22>
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